The present invention relates to a semiconductor device and is suited for use, for example, in a semiconductor device using a nitride semiconductor.
Since a nitride semiconductor such as gallium nitride (GaN) has a band gap greater than that of silicon (Si) and has a great critical electric field, a high-breakdown-voltage and low-loss power device is likely to be realized. Such a power device is however a normally-on type so that a gate structure providing the device with normally-off characteristics is under investigation.
For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2009-9993) discloses a semiconductor device having, on a silicon pin diode thereof, an HEFT using an AlGaN/GaN hetero junction structure. The source electrode of this semiconductor device is coupled to a p type silicon layer via a trench penetrating through a barrier layer, a channel layer, and a buffer layer and reaching the p type silicon layer.
Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2007-103451) discloses a normally-off type semiconductor device having a stacked portion comprised of an Al0.2Ga0.8N layer, a GaN layer, and an InGaN layer.
Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2009-200096) discloses a nitride semiconductor device featuring a small leakage current produced when a high bias voltage is applied and a small loss when the device is turned off.